All-dry synthesis of self-supporting thin Li10GeP2S12 membrane and interface engineering for solid state lithium metal batteries

• All-dry synthesis of thin (~100 μm) sulfide electrolyte. • High room-temperature ionic conductivity (3.6 × 10 -4 S cm −1 ). • Excellent interface stability by an in-situ polymer interlayer. • Outstanding cell performance of as-prepared composite LGPS electrolyte. Sulfide solid electrolytes have attracted much attention for next generation lithium batteries due to their high ionic conductivity and low grain boundary impedance. However, they generally suffer poor processability into a thin membrane applied in high energy–density batteries and usually unstable with some organic solvents and moistures. Furthermore, the huge interfacial resistance, originated from the side reactions at electrode/electrolyte interfaces, deteriorates the electrochemical performance of batteries. Here, we develop a thin (~100 μm) Li 10 GeP 2 S 12 (LGPS) membrane composed by trace polytetrafluoroethylene (PTFE) binder with LGPS powders through all-dry grinding method and reinforced with a nylon mesh. Thin LGPS can not only reduce the cost, but also improve the energy density of the battery. Moreover, the interface stability between the LGPS electrolyte and electrodes has been significantly enhanced by employing an in-situ gel polymerized electrolyte (GPE) on lithium metal anode, and coating LiNbO 3 on LiNi 0.5 Mn 0.3 Co 0.2 O 2 (LNO@NCM532) separately. As a result, the prepared LNO@NCM532|C-LGPS|GPE|Li batteries reveal satisfying discharge specific capacities and good cyclic stabilities at room temperature.